Fashion e-commerce has treated sizing technology as an obvious solution to an obvious problem: if customers can choose the right size more accurately, returns should fall.
A large 2025 study complicates that assumption.
THE RESEARCH
Researchers analyzed 496,365 items ordered by 75,707 customers from 113 countries on a high-end fashion e-commerce platform. The platform’s size finder used customer information such as weight, build, hips, waist, shoulders, proportions and body shape.
The surprising result: customers who used the size finder were 0.65% more likely to return an item, not less. In the study’s predictive models, size-finder use was also among the less important variables for forecasting returns.
So was the tool useless?
No. The same analysis found a relationship between greater use of the size finder and higher subsequent customer lifetime value: a 7.51% increase in the following quarter and 5.53% in the quarter after that for each unit quarterly increase in use described by the researchers.
That creates a more sophisticated interpretation. A sizing tool can increase confidence and engagement without eliminating the fundamental uncertainty of fashion fit. Customers may buy more, experiment more, or become more comfortable making decisions—even while returns remain part of the behavior.
The real problem is multidimensional fit
A nominal size is not the same as fit. Two people with similar measurements may prefer different levels of compression, rise, length, support or ease. Fabric stretch, pattern geometry, intended silhouette and subjective comfort all influence whether a product feels “right.”
For activewear, movement makes the problem even more complex. Static measurements cannot fully communicate what happens when someone squats, runs, bends, sits or wears a piece for several hours.
KEY SIGNALS TO SAVE
- 496,365 fashion items were included in the study.
- Size-finder users were slightly more likely to return, not less.
- Greater size-finder use was nevertheless associated with higher subsequent customer lifetime value.
THE PALM POINT OF VIEW
The lesson is not “do not build sizing tools.” It is that fit cannot be outsourced to a calculator. Better commerce requires richer product descriptions, real garment measurements, clear model context, honest stretch/support language, movement photography and a feedback loop that improves future products.